Knowing the Energy of a photon, what is the charge of a species?

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Discussion Overview

The discussion revolves around a homework problem involving the energy of a photon and its relation to the charge of a one-electron species, specifically an atom or ion transitioning from the ground state to an excited state. The focus is on understanding the calculations related to energy levels and the implications for charge determination.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant presents a calculation using the energy equation for a one-electron atom, leading to a derived nuclear charge of approximately +3.
  • Another participant questions the interpretation of the charge being asked, suggesting that the charge of the ion is different from the nuclear charge.
  • There is a mention of effective charge due to shielding, proposing that the effective charge might be around +2.
  • Clarification is provided that the question specifically asks for the charge of the ion, not the nucleus.
  • Participants discuss the implications of the calculated nuclear charge on the overall charge of the ion, with one concluding that a single electron would result in a charge of +2.
  • One participant acknowledges the difference between their initial equations and the final interpretation of the charge.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the interpretation of the charge being asked for, with some confusion about the relationship between nuclear charge and ion charge. There is no consensus on the correct interpretation, as differing views on the effective charge and the calculations presented are evident.

Contextual Notes

Participants highlight potential misunderstandings regarding the question's requirements and the calculations involved, particularly the distinction between nuclear charge and ion charge. There are unresolved aspects regarding the assumptions made in the calculations and the implications of shielding.

Who May Find This Useful

This discussion may be useful for students studying atomic physics, particularly those grappling with concepts of energy levels, ionization, and charge calculations in one-electron systems.

brbrett
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Homework Statement


An atom or ion with only one electron is excited from the ground state to the first excited state (n = 2) with a photon of 1.47E-17 J of energy. What is the charge on the one-electron species?
A. 0
B. +1
C. +2
D. +3
E. +4

Homework Equations


E=-(2.18E-18)(Z2)/(N2)

The Attempt at a Solution


I plugged in the information given into the equation:

(1.47E-17)=(-2.18E-18)(Z2)((1/4)-1)

With some algebra, I got Z=2.998, which may as well be a charge of +3.
However, according to the answer key, the correct answer is, in fact, +2 (C).
I would appreciate any guidance as to where I might be going wrong with this problem. :)
 
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What is the charge of the ion as a whole if the charge of the nucleus is 3?
 
Due to shielding, the effective charge would be about +2? I think I kinda see that maybe my calculations weren't wrong, but that I didn't understand the question right, but I still don't really get it.
 
You calculated Z, but Z is not what the question asks about. It asks you to calculate charge of the ion, not of the nucleus.
 
Ah, so then because I calculated the nucleus' charge to be +3, with a single electron there would be a charge of +2? That would make a lot of sense. Then I assume I didn't make any mistakes in solving for charge of the nucleus to figure out the ion's charge? Thanks!
 
Looks OK, although your first equation and the second equation are different.
 
Thanks!
 

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